1. Field of the Invention
The present invention relates to a photoelectric conversion element, a dye-sensitized solar cell, and a metal complex dye used in the same.
2. Description of the Related Art
Photoelectric conversion elements are used in various photosensors, copy machines, solar cells, and the like. The photoelectric conversion elements have been put to practical use in the form of photoelectric conversion elements adopting various modes, such as photoelectric conversion elements using metals, photoelectric conversion elements using semiconductors, photoelectric conversion elements using organic pigments or dyes, or photoelectric conversion elements as a combination of these. Particularly, because solar cells using inexhaustible solar energy do not require fuel and use inexhaustible clean energy, full-scale commercialization of solar cells is highly anticipated. Among solar cells, silicon-based solar cells have been researched and developed for a long period of time, and are becoming increasingly popular by the political support of each country. However, because silicon is an inorganic material, the throughput and molecular modification thereof are inevitably limited.
For this reason, dye-sensitized solar cells are being strenuously researched. Particularly, the research was fueled by the results of research conducted by Graetzel et al. of EPFL of Switzerland. By adopting a structure in which a dye composed of a ruthenium complex is fixed to the surface of a thin film of porous titanium oxide, Graetzel et al. realized photoelectric conversion efficiency equivalent to that of amorphous silicon. As a result, dye-sensitized solar cells instantly drew the attention of researchers all over the world.
U.S. Pat. No. 5,463,057A describes a dye sensitized photoelectric conversion element using semiconductor particles sensitized by a ruthenium complex dye by applying the aforementioned technique. Since then, in order to improve the photoelectric conversion efficiency, ruthenium complex-based sensitizing dyes have been continuously developed (see US2010/0258175A).